Field
The present disclosure relates to variable optical attenuators and, more specifically, to variable optical attenuators with a diffracting prism and prism positioning system.
Technical Background
Variable optical attenuators (VOAs) are known and widely used in fiber optical communication systems. For example, one type of variable optical attenuator is based on an MEMS actuator that operates via a resilient mechanical hinge designed into a MEMS chip. When an electrical signal is applied to the MEMS chip the mechanical hinge may be moved into attenuating position such that a portion of an optical signal is blocked. Once the electrical signal is terminated, the mechanical hinge moves to a non-attenuating position in which light from a fiber optic is not blocked. In the alternative, the mechanical hinge can be oriented such that the supply of an electrical signal to the MEMS chip places the mechanical hinge into the non-attenuating position and when the electrical signal is terminated the mechanical hinge returns to the attenuating position. Such variable optical attenuators are relatively complex and require MEMS chip manufacturing.
Another type of variable optical attenuator is a neutral density (ND) filter that reduces or modifies the intensity of all wavelengths or colors of a light signal equally. A variation of the neutral density filter is a gradient neutral density filter that only blocks certain wavelengths of an optical signal. However, manufacture of a neutral density filter, particularly a gradient neutral density filter, requires complex processes and equipment. Also, an optical signal passing through a gradient neutral density filter may be impaired by the reflection of the optical signal surfaces of shapes or particles contained in the filter. Accordingly, an improved variable optical attenuator is desired.